1. Technical Field
The present invention relates to an energy dispersive X-ray analyzer that is used being attached to a scanning electron microscope and a method for energy dispersive X-ray analysis.
2. Description of the Related Art
In energy dispersive X-ray analyzers to be attached to a scanning electron microscope, X-rays that are generated by irradiating a sample with an accelerated electron beam are acquired by the energy dispersive X-ray analyzer and used for quantitative/qualitative analysis of a minute portion of the sample. For another example, a two-dimensional X-ray intensity image is obtained together with a scanning electron microscope image by scanning a sample two-dimensionally with an accelerated electron beam and acquiring generated X-rays being synchronized with the scanning.
Conventionally, for example, JP-A-2000-214108 discloses an area analysis method for a sample having an arbitrary shape that employs an electron probe microanalyzer (EPMA). A sample embedded body is used in which a sample is embedded in an embedding material. An area analysis is performed on a sample having an arbitrary shape by executing a step of setting an analysis target region in a sample embedded body and dividing the analysis target region into plural small divisional regions, a step of setting (selecting) small divisional regions each containing part of the sample, and a step of measuring and analyzing the thus-set small divisional regions successively and connecting analysis results of the respective small divisional regions.
JP-A-H05(1993)-026826 discloses a method for performing a quantitative analysis and a film thickness measurement by an X-ray spectroscopic method using an EPMA or the like in a case that a substrate and a thin film of a thin-film sample contain the same element and the constituent elements of the substrate and the thin film are known. This analyzing method is a thickness measuring method using a standard sample and is performed in the following manner. A ratio (X-ray intensity ratio) between an intensity of characteristic X-rays of a component element that are radiated from a thin-film sample (whose constituent elements are known) excited by an electron beam accelerated at a proper acceleration voltage and an intensity of X-rays radiated from a simple substance sample of the component element excited by an accelerated electron beam of the same kind is measured actually in advance (the component element should be such as to enable such an actual measurement). An X-ray intensity ratio of an element whose X-ray intensity ratio cannot be measured by an actual measurement is determined from the above-measured X-ray intensity ratio of the other element and a chemical bonding form of the measurement-incapable element and the other element. A thickness of the thin-film sample is calculated from X-ray intensity ratios of all component elements according to a particular formula, and concentrations of the respective component elements are calculated from ratios between the X-ray intensity ratios.
The above described conventional technique may have the following problems to be solved. That is, whereas the above-described techniques enable recognition of a planar element distribution by observing a two-dimensional X-ray intensity image, they do not allow users to determine an element distribution in the depth direction.
The technique disclosed in JP-A-H05(1993)-026826 relates to a thickness measurement using a standard sample and does not allow users to determine an element distribution in the depth direction.
A method for determining whether or not an element is distributed uniformly in the thickness direction is available in which a cross section of a sample is formed and an element distribution in the depth direction is recognized by performing a measurement on the cross section. However, observation of a cross section of a region of attention requires a dedicated facility and an element distribution in the depth direction can be determined only after doing long-time work of forming a cross section. As such, this method may have a problem that it takes much time and labor.